Develop Reference

Linq statement in C# to extract data from XElement

I have a List containing elements like this:
{<d:element m:type="SP.KeyValue" xmlns:m="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata" xmlns:d="http://schemas.microsoft.com/ado/2007/08/dataservices">
<d:Key>Path</d:Key>
<d:Value>https://my.home.site.com</d:Value>
<d:ValueType>Edm.String</d:ValueType>
</d:element>}
I'd like help to discern the Linq statement required to extract only the "https://my.home.site.com" values from said List<>. The catch here is that we cannot only use the <d:Value> because only XElements in this list that has a <d:Key> value of Path, like in the example above, actually contain URLs in the <d:Value> key.
Does anyone know the magic Linq statement that would perform said data extract?

Assuming your data is coming from an XML file similar to this:
<?xml version="1.0"?>
<root xmlns:m="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata" xmlns:d="http://schemas.microsoft.com/ado/2007/08/dataservices">
<d:element m:type="SP.KeyValue">
<d:Key>Path</d:Key>
<d:Value>https://my.home.site.com</d:Value>
<d:ValueType>Edm.String</d:ValueType>
</d:element>
<d:element m:type="SP.KeyValue">
<d:Key>NotPath</d:Key>
<d:Value>https://my.home.site.com</d:Value>
<d:ValueType>Edm.String</d:ValueType>
</d:element>
</root>
The following code:
XElement root = XElement.Load("Some file");
List<string> urls;
//Query Syntax
urls = (from e in root.Elements(d + "element")
where e.Element(d + "Key").Value == "Path"
select e.Element(d + "Value").Value);
//Or
//Method Syntax
urls = (from e in root.Elements(d + "element")
where e.Element(d + "Key").Value == "Path"
select e.Element(d + "Value").Value).ToList();
Console.WriteLine(string.Join(",", urls));
Will result in (note that it ignores the "NotPath" key):
https://my.home.site.com
You can check out a live example here and check out this for more XElement information.

if you actually have a List of XElement:
var list = new List<XElement>(); //however you get your XElement collection
var values = list.Where(x => x.Elements().First(e => e.Name.LocalName == "Key").Value == "Path")
.Select(x => x.Elements().First(e => e.Name.LocalName == "Value").Value)
if you have an XDocument, you'd just modify the beginning of the query slightly.

I think that problem if with naespace declaration. Try this:
string xml = "<d:element m:type=\"SP.KeyValue\" xmlns:m=\"http://schemas.microsoft.com/ado/2007/08/dataservices/metadata\" xmlns:d=\"http://schemas.microsoft.com/ado/2007/08/dataservices\">"+
"<d:Key>Path</d:Key>"+
"<d:Value>https://my.home.site.com</d:Value>"+
"<d:ValueType>Edm.String</d:ValueType>"+
"</d:element>";
XDocument xmlObj = XDocument.Parse(xml);
XNamespace ns_d = "http://schemas.microsoft.com/ado/2007/08/dataservices";
var result = xmlObj.Descendants(ns_d + "Value").Select(x => x.Value);

Retrieving XML attributes of unknown quantity

I have requirement to read an XML file. I've never done anything with XML so it's all new territory for me. Please refer to the below XML sample.
-
<GPO xmlns="http://www.microsoft.com/GroupPolicy/Settings" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">+
<Identifier>
<Name>GB Local Server Access</Name>
<IncludeComments>true</IncludeComments>
<CreatedTime>2011-08-03T11:58:18</CreatedTime>
<ModifiedTime>2011-08-03T12:13:41</ModifiedTime>
<ReadTime>2014-10-21T11:32:49.5863908Z</ReadTime>+
<SecurityDescriptor>----------------------------
<FilterDataAvailable>true</FilterDataAvailable>-
<Computer>
<VersionDirectory>18</VersionDirectory>
<VersionSysvol>18</VersionSysvol>
<Enabled>true</Enabled>-
<ExtensionData>-
<Extension xsi:type="q1:SecuritySettings" xmlns:q1="http://www.microsoft.com/GroupPolicy/Settings/Security">-
<q1:RestrictedGroups>-
<q1:GroupName>
<SID xmlns="http://www.microsoft.com/GroupPolicy/Types">S-1-5-21-1547161642-1214440339-682003330-1141792</SID>
<Name xmlns="http://www.microsoft.com/GroupPolicy/Types">CRB\DKCPHGITSCOM</Name>
</q1:GroupName>-
<q1:Memberof>
<SID xmlns="http://www.microsoft.com/GroupPolicy/Types">S-1-5-32-544</SID>
<Name xmlns="http://www.microsoft.com/GroupPolicy/Types">BUILTIN\Administrators</Name>
</q1:Memberof>
</q1:RestrictedGroups>-
<q1:RestrictedGroups>-
<q1:GroupName>
<SID xmlns="http://www.microsoft.com/GroupPolicy/Types">S-1-5-21-1547161642-1214440339-682003330-1151</SID>
<Name xmlns="http://www.microsoft.com/GroupPolicy/Types">CRB\GB Administrators</Name>
</q1:GroupName>-
<q1:Memberof>
<SID xmlns="http://www.microsoft.com/GroupPolicy/Types">S-1-5-32-544</SID>
<Name xmlns="http://www.microsoft.com/GroupPolicy/Types">BUILTIN\Administrators</Name>
</q1:Memberof>
</q1:RestrictedGroups>
Please could you advise on the simplest method that I can use that will allow me to drill down to GPO.Computer.ExtensionData.Extension.RestrictedGroups and then FOR EACH instance of RestrictedGroups return the value of GroupName.Name and MemberOf.Name. I can then incorporate the logic to get this data into an array of some sort ready to be output.

You should use LINQ to XML.
Something like:
//preparing the reusable XName instances:
var q1Namespace = "http://www.microsoft.com/GroupPolicy/Settings/Security";
var groupNameElementName = XName.Get("GroupName", q1Namespace);
var memberOfElementName = XName.Get("Memberof", q1Namespace);
var nameElementName = XName.Get("Name", "http://www.microsoft.com/GroupPolicy/Types");
var data = XDocument.Load(filePath)
.Descendants(XName.Get("RestrictedGroups", q1Namespace))
.Select(group =>
new
{
GroupName =
group.Descendants(groupNameElementName)
.Select(gn => gn.Element(nameElementName).Value)
.FirstOrDefault(),
MemberOfName =
group.Descendants(memberOfElementName)
.Select(gn => gn.Element(nameElementName).Value)
.FirstOrDefault()
});
Then use it in foreach loop:
foreach (var d in data)
{
Console.WriteLine("Group name: {0}, member of name: {1}", d.GroupName, d.MemberOfName);
}
If you'd like to make it safe and provide default values for the names, use something like the below instead of the Select call which finds the Name element:
...
.SelectMany(gn => gn.Elements(nameElementName))
.Select(elem => elem.Value ?? "Name not found")
.DefaultIfEmpty("Name not found")
.FirstOrDefault()
This way you will protect yourself from the cases where the Name element does not exist or has no value.

How do I parse text from complex type xml in c# using XDocument?

<?xml version="1.0" encoding="UTF-8"?>
<meta>
<field type="xs-string" name="AssetId">TF00000002</field>
<field type="xs-string" name="Title">TitleOfAsset</field>
</meta>
I have this XML loaded in to a XDocument using the function
XDocument doc = XDocument.Parse(xmlData)
However, I want to be able to retrieve the text fields "TF00000002" and "TitleOfAsset" ... How do I go about doing this?
templateMetaData.assetID = doc
.Descendants()
.Where(p => p.Name.LocalName == "AssetId")
.ToString();
returns:
System.Linq.Enumerable+WhereEnumerableIterator`1[System.Xml.Linq.XElement]
Can anyone shine a light on this?

In your query, you are calling ToString on an IEnumerable<XElement> which will never give you the expected result, instead look for field elements under your Root and get their value:
var values = doc.Root
.Elements("field")
.Select(element => (string)element);
If you want to access your values using the name attribute you can use Dictionary:
var values = doc.Root
.Elements("field")
.ToDictionary(x => (string)x.Attribute("name"), x => (string)x);
Then you can access the value of AssetId:
var id = values["AssetId"];

Linq to XML Descendants can't read part of xml

I have XML document like this
<document>
<indexroot>
<type>type</type>
<model>model</model>
</indexroot>
<root>
<model_type1>model type 1</model_type1>
<model_type2>model type 2</model_type2>
</root>
</document>
And a linq to xml code:
var elements = (from element in pdb.Descendants()
select new
{
type = (string)element.Element("type") ?? "-",
model= (string)element.Element("model") ?? "-",
model_type1= (string)element.Element("model_type1") ?? "-",
model_type2= (string)element.Element("model_type2") ?? "-"
}).FirstOrDefault();
I get type and a model variables, but it seems I can't reach model_type1 and model_type2, now I understand that this happens because indexroot and root tags, amd if I seperate those tags into diffrent linq to xml code blocks with Descendants("indexroot") and Descendants("root"), everything works fine, but I wan't them in one block, is it possible to achieve that, and how?

You need to navigate down the XML heirarchy for each element you are trying to extract.
This is because the Element method only looks at direct children, not all descendants of a node. From the documentation:
Gets the first (in document order) child element with the specified XName.
One implementation using just Linq-to-XML might be:
xml = "<document>" +
"<indexroot>" +
" <type>type</type>" +
" <model>model</model>" +
"</indexroot>" +
"<root>" +
" <model_type1>model type 1</model_type1>" +
" <model_type2>model type 2</model_type2>" +
"</root>" +
"</document>";
XDocument doc = XDocument.Parse(xml);
var newItem = (from element in doc.Descendants("document")
select new
{
Type = (string)element.Element("indexroot").Element("type") ?? "-",
Model = (string)element.Element("indexroot").Element("model") ?? "-",
ModelType1 = (string)element.Element("root").Element("model_type1") ?? "-",
ModelType2 = (string)element.Element("root").Element("model_type2") ?? "-",
}).FirstOrDefault();
Console.WriteLine(newItem);

C# reading values of elements from an XML tree

I am trying to read some values of specific elements in an XML document, such as the values of <main><alpha>, <main><beta><epsilon> and <main><gama><delta>.
<?xml version="1.0" ?>
<main>
<alpha>One</alpha>
<beta>
<delta>DeltaValueFromBeta</delta>
<epsilon>EpsilonValueFromBeta</epsilon>
<phi>PhiValueFromBeta</phi>
</beta>
<gamma>
<delta>DeltaValueFromGamma</delta>
<epsilon>EpsilonValueFromGamma</epsilon>
<phi>PhiValueFromGamma</phi>
</gamma>
</main>
I can get the values using code like this:
XDocument doc = XDocument.Load("Sample.xml");
var quiz = from elements in doc.Elements("main").Elements("beta").Elements("epsilon")
select elements;
foreach (var item in quiz)
{
string sValue = (string) item.Value;
textBox1.AppendText(sValue);
}
Is there a more direct way to select the element values I need, without having to use a foreach loop?
Thanks
Nick

XPath is another option for direct access to a node. This reference may assist you.
How to get values from an XML file matching XPath query in C#
Edit to add to text box without foreach where result = XPath query result collection:
textbox1.AppendText(result.Select(x => x.Value));
XPath allows for dynamic path building a little easier than LINQ queries.

You can do it in your linq query:
var quiz = (from elements in doc.Elements("main").Elements("beta").Elements("epsilon")
select (string)elements).ToList();
It will give you value list.And you can append your text without using foreach:
StringBuilder sb = new StringBuilder();
var values = quiz.Select(x => sb.Append(x));
textBox1.AppendText(sb.ToString());
Or better way:
var text = doc.Descendants("epsilon")
.Select(x => (string)x)
.Aggregate((x,y) => x + y);
textBox1.AppendText(text)

textBox1.AppendText(quiz.Select(x => x.Value).Aggregate((s, s1) => s + s1));

Use the following so you do not have to use a foreach:
IEnumerable<string> values = quiz.Select(x => x.Value);
Or all in one:
IEnumerable<string> values = doc.Elements("main").Elements("beta").Elements("epsilon").Select(x => x.Value);
textBox1.AppendText(values.Aggregate((i, j) => i + j));